The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Portable devices with positioning modules, such as smartphones, tablet computer, or GPS receivers, commonly use multiple wireless signals to obtain a “position fix,” or an estimate of the current geographic location. Generally speaking, a positioning module calculates the position fix by analyzing the time multiple signals take to reach the portable device from known locations. Portable devices may use signals from positioning satellites, such as those used in the global positioning system (GPS), mobile network transceivers, or wireless local area network (WLAN) routers, such as those used in a Wi-Fi-based positioning system (WPS), to facilitate positioning calculations.
Regardless of the signal source, portable devices attempting to calculate a position fix are prone to positioning errors due to obstructions along the signal paths. These obstructions may be atmospheric or terrestrial. Terrestrial objects, such as buildings or trees, may result in multipath reflections, while layers of the atmosphere may decelerate and refract signals, for example.